Rotary printing machine



June15, 1937. I GmRAL'L 2,083,754

BOT ARY PRINTING MACHINE Filed 001:. 51, 1934 2 Sheets-Sheet 1 June 15, 1937. TURRALL I 2,083,754

ROTARY PRINTING MACHINE Filed 001;. 31, 1934 2 Sheets-Sheet 2 33 INVENTOR.

Patented June 15, 1937 UNITED STATES PATENT OFFICE ROTARY PRINTING MACHINE George Turrall, London, England, assignor to R.

Hoe & 00., Inc., New York, N. Y., a corporation of New York Application October 31, 1934, Serial No. 750,793 In Great Britain November 29, 1933 Claims.

The ends of the blankets on the impression cyl-.

inders of the couples are received within recesses formed in the cylinders and these recesses are so staggered that as the cylinders rotate the recesses and one or other of the bars register.

It will be apparent that the position of the margin bars determines the position of the plates circumferentially of the cylinder and in the case of a multi-couple machine the corresponding bars of the various couples must be in exactly corresponding positions in order to obtain accurate page or other register on a Web printed by the couples.

It is frequently required that one or other of a plurality of associated couples shall be arranged to rotate at one time in one direction and at another time in the reverse direction: such a condition occurs for example when two (or more) associated couples are required at one time to print I on opposite sides of a web and at another time to print on the same side of a web, this latter condition occurring for example in colour printing. It will be apparent that reversal in the direction of one couple relatively to an associated couple destroys the correspondence between the margin bars of the couples for if one bar be regarded as leading another bar in one direction of rotation, it will be lagging in the other direction of rotation.

In order to provide for a re-positioning of the bars of the couple (or of both couples) it has been common in the example referred to, to render detachable the bars of one end of the plate cylinder so that these bars can be removed from a position on one side of the bars of the other end and re-secured in a position on the opposite side of the bars of the said other end: for example, if the bars of one end be regarded as leading the bars at the other end by 120 they can be detached and re-secured so as to be 120 behind (the direction being here considered constant) the said other bars.

In order correspondingly to adjust the position of the recess at one end of the co-operating impression cylinder it was common to provide two recesses in positions which corresponded to the two alternative positions of the margin bar with which it has to register, i. e. in the example referred to, the slots would respectively be in advance of and behind the slot at the other end of the cylinder; there were also provided two detachable pieces arranged each to lit in one or other of the two recesses, one piece being slotted to receive the ends of the blanket while lll the other piece was arranged to blank-off or cover the recess and to provide a smooth or unbroken continuation of the periphery of the impression cylinder. Thus, when the couple was required to run in one direction the slotted piece was inserted in one of the recesses so as to register with one of the adjustable bars, the other piece filling the other recess, while when the couple was required to run in the reverse direction, the pieces were interchanged to correspond with the adjustment effected on the bars. In order to obtain proper printing it is imperative that the surface of the filling piece should form a true continuation of the surface of the impression cylinder (the slightest departure from this critical condition resulting in bad printing due to the change in impression pressure). It will therefore, be obvious that as the filling piece is required to fit either of two slots with exactly the same precision if proper printing is to be obtained the practical difliculties are very great and entail considerable expense; moreover, the critical position of the filling piece may vary during the production process and even during transport and in these conditions the setting operation would have to be re-effected.

The main object of the present invention is to provide an arrangement which will enable these practical difficulties to be avoided in a manner which is simple and reduces the cost of production.

According to the present invention, the impression cylinder is formed with a plurality of recesses which are spaced apart circumferentially of the cylinder and in each of some or all of the recesses is slidably mounted a filling piece whose outer surface is shaped to conform to the contour of the periphery of the impression cylinder. The number of slots and their length and the number of sliding pieces and their length or relative length will depend upon the number of sets of margin bars on the plate cylinder; moreover, the angular separation of the slots circumferentially of the cylinder will depend upon the angle of stagger between the sets of margin bars: Whatever the actual disposition, the arrangement is such that the relative positions of the unblanked parts of the recesses can be interchanged by the sliding pieces to enable a lead to be obtained in either direction of rotation. It will be seen that an arrangement according to the invention avoids the difficulties due to the provision of filling pieces which had to fit with precision in a plurality of recesses, for it is comparatively simple to fit a member (i. e. the sliding piece) to one recess only. For example when the invention is applied to an impression cylinder arranged for co-operation with a plate cylinder having two sets of margin bars, the bars of one set being staggered with f respect to the bars of the other set and one set of bars extending from one end of the plate cylinder to the middle thereof and the other set extending from the other end to the middle, there would be provided two recesses in the impression cylinder: the recesses would be parallel with the axis of the cylinder and each would extend throughout the length thereof, the recesses being 120 apart circumferentially of the cylinder: a filling piece would be located in each recess and the length of each piece would be equal to one half the length of the recess.

When the cylinders are set to run in one direction, one of the pieces would be at one end of its recess and the other piece at the other end, thus leaving unblanked two recess portions spaced apart circumferentially by 120 and one extending through one half of the cylinder and the other through the other half of the cylinder so that one recess has a lead of 120 with respect to the other to correspond with the lead of one set of margin bars relatively to the other set. If now it is desired to reverse the direction of rotation of the cylinders, the respective pieces are slid to opposite ends of their recesses: thus the unblanked portions of the recesses are reversed thereby enabling that end of the cylinder which had a recess leading in one direction to have also a recess which leads in the reverse direction of rotation.

If the invention be applied to an impression cylinder arranged to co-operate with a plate cylinder having three staggered sets of margin bars of equal length, then the impression cylinder would be provided with three recesses, the two outer ones of which would extend throughout the length of the cylinder while the middle recess would be equal to the length of the central margin bars, the recesses being spaced from each other by an angular distance equal to the angle of stagger. In the two outer recesses would be positioned a filling piece whose length would be equal to twice the length of a margin bar so that by sliding these pieces to respectively opposite ends of their recesses the unblanked portions of the recesses could be interchanged.

It will be appreciated that in each of the recesses there is provided means for holding one end of a blanket and for pulling-in the other end of the blanket to tighten it on to the periphery of the cylinder and it will also be evident that when changing-over, the blankets will have to be released and repositioned.

It will, of course, be understood that the margin bars will be re-positioned in the usual manner and therefore, in order to bring the interchanged unblanked recesses into register with the respective bars it is necessary to provide for the turning of the impression cylinder relatively to its plate cylinder through an angle equal to the angle of stagger. This can be effected by connecting the impression cylinder to the plate cylinder through a pin clutch which can be moved into clutching osition in only two positions, these positions being spaced apart through an angle equal to the angle of stagger. Provision may also be made for the adjustment of the two cylinders of one couple relatively to another or other associated couple or couples due to change in the direction of run of a web; the arrangement preferably is of the kind described and claimed in the specification of British Patent No. 395,413 issued to Quick and Ball, dated January 16, 1932 and conveniently also the pin clutch referred to for effecting adjustment of the impression cylinder relatively to the plate cylinder is of the form described in the said specification.

The invention is illustrated in the accompanying drawings in which Figures 1 and 2 are diagrammatic views showing the plate and impression cylinders separated from one another for the sake of clearness: Figure 3 is an elevation partly in section. of the two cylinders, Figure 4 a detail sectional elevation, Figure 5 a plan view of the two cylinders showing the driving arrangement therefor and Figures 6 and '7 detail views of clutch mechanism, Figure 6 being an end elevation and Figure 7 a longitudinal section.

Referring firstly to Figures 1 and 2, i indicates diagrammatically a plate cylinder and 2 diagrammatically indicates an impression cylinder, it being understood that these two cylinders are shown broken and also separated from one another for the sake of clearness but would actually co-oporate as shown in Figure 3. The plate cylinder I has a front pair of margin bars 3, 4 which are spaced apart and operate to position front printing plates (not shown) against circumferential movement: this cylinder also has a rear pair of margin bars 5, 6 which are also spaced 180 apart and similarly position rear printing plates, the rear bars being staggered with respect to and lagging behind the front bars through an angle which as shown is 120.

The impression cylinder 2 is provided with a front blanket l and a rear blanket 8: The ends of the front blanket l' are received within a recess 9 formed in the front half of the impression cylinder, and this recess is arranged to register (as the two cylinders i, 2 rotate in the directions shown in. Figure 1) with the front margin bar 3, it will be appreciated that such registration is necessary in order to avoid loss in impression pressure during printing as would of course occur if the recess 9 were positioned to register with a part of the printing plates positioned between the margin i bars 3 and 4. The ends of the rear blanket 8 are received within a recess iii formed in the rear half of the impression cylinder this recess being arranged to register with the rear margin bar 5 and hence the two recesses are spaced 120 apart as indicated by e in the drawings. It will thus be seen that, as the two cylinders rotate in the direction shown in Figure 1, the recesses 9 and I0 and the front and rear margin bars 3 and 5 will successively register, first the front bar 3 and the recess 9 and then (120 later) the rear bar 5 and the recess ID, the bar 3 thus leading the bar 5 by 120 indicated by on in the drawings.

It will be apparent that, if the direction of rotation be reversed, the bars 3, 4 of the front of the plate cylinder I would in the absence of change, la behind those of the rear end of the cylinder. In order, however, that the bars of the front end of the impression cylinder shall lead those at the rear by 120 when the direction of rotation is reversed so as to be in the directions shown in Figure 2, the bars 5, 6 would be removed from the positions they occupy in Figure 1 and resecured in the position shown in Figure 2, i. e. the bars 5, 6 would be moved through 240 from one position 120 on one side of the front bars 3, 4 to a position 120 on the other side of the front bars. In order now to provide for a repositioning of the recesses to register with the bars 3 and 5 in their new positions the recess 9 is continued at 9a to extend through the rear half of the impression cylinder and the recess I 0 is continued at Illa to extend through the front half of this cylinder: In each of the recesses 9, 9a and I0, Illa there is provided filling pieces I I, I2 respectively, the filling pieces being of substantially one half the length of each recess and of dimensions such as to blank off that part of its recess in which it is contained. It will now be seen that when the piece I 2 is in the front half of the impression cylinder and the piece I I is in the rear half of the cylinder (as shown in Figure 1) the condition described with reference to Figure l is obtained: When, however, the blankets have been removed and the piece I2 is slid to occupy the rear part II) of the recess I ll, Ina and the piece II is slid to occupy the front part 9 of the recess 9, 9a (as shown in Figure 2) the recess openings (i. e. the unblanked parts) are reversed so that whereas in one position (i. e. that shown in Figure 1) the front part 9 of the recess 9, 9a leads in the direction of rotation shown, the rear part II! of the recess I0, I 0a in the other position (i. e. that shown in Figure 2) due to the reversal, the unblanked recess, i. e. part Illa at the front of the cylinder leads the unblanked recess, i. e. the part Be at the rear end despite the reversal in the direction of rotation.

It is now merely necessary that the impression cylinder be turned back relatively to the plate cylinder so as to enable the recesses Set, I Ila to register with the bars 3, 5 in their new position, the angle through which this turning is effected being equal to the angle of stagger, i. e. 120 in the example given.

The invention thus provides a simple and reliable means for enabling a printing and impression cylinder to be run in either direction with a margin bar which leads by a certain angle in one direction of rotation to lead by the same angle in the other direction of rotation while avoiding the practical difliculties referred to as arising from using a detachable filling piece, for it will be seen that the filling pieces in accordance with the invention are required only each to be a sliding fit in a single recess.

Referring now to Figure 3, which illustrates a practical embodiment of the invention, the front margin bars 3, 4 are indicated by the sectioned parts 3, 4 and the rear margin bars 5, 6 by the unsectioned parts 5, '6 and the two cylinders I, 2 are arranged to run in the direction indicated by the arrows, this direction corresponding to that of Figure 1. The filling piece I2 which in the direction of rotation referred to is in position to fill the front half Ilia of the recess Ill, Illa is shown in section while the filling piece I I which fills the rear half 9a of the recess 9, 9a is shown in elevation: each recess 9, 9a and I0, Illa opens into an enlarged recess indicated at It, I 4 respectively and each recess i3, I4 is provided with two sets of devices enabling a blanket to be secured to the cylinder: Each device comprises pins I5 which receive eyelets in the end of the blanket I or 8 and a rotatable bar I6 to which the other end of the blanket is secured by a clamping piece IIia, the. bar having a ratchet wheel I'I engaged by a ratchet I8: This mechanism is commonly provided for securing a blanket to a cylinder, and further description thereof is believed to be unnecessary: It is, however, to be observed that the device at the front half of the recess I3 is on one side of the recess while the device at the rear half of the recess I3 is at the other side: Similarly the device in the front and rear halves of the recess I4 are on opposite sides of the recess. The object of thus staggering the devices is to enable the blankets to be secured so that any frictional drag exerted on the blankets by the plates on the printing cylinder will operate to pull the blanket more tightly on to the pins I5: Thus it will be seen by reference to Figure 3 that the front and rear blankets 'I, 8 are secured to pins I5 which are on that side of the recesses I3, I4 which lags the rotation of the cylinder 2: When, however, the blankets are removed and the filling pieces II, I2 slid to opposite ends of their recesses 9, 9a and I0, I Ila to provide for reversal in the direction of rotation, then the blankets would be secured to the devices which are on the opposite side of the recesses I3, I4 as compared with the devices from, which the blankets were removed and thus lag on the recesses I3, 54 in the new direction of rotation.

In order to position the filling pieces II, I2 against radial movement, the pieces are provided with ribs I9, 20 which enter grooves out in the walls of the recess, the ribs and grooves constituting a guide way for the pieces: In order also releasably to position the pieces against endwise movement, one end of each piece is formed with a transverse groove which receives a locking plate ZI (only one of which is shown in Figure l) which is pivotally mounted at 22 on the end of the cylinder so that it can be swung into and out of the groove, a bolt 23 being provided for locking the plate.

As has previously been stated, it is necessary to turn the impression cylinder 2 with respect to the plate cylinder I to bring the recesses 9, 9a, Ill, Illa into register with the margin bars: As is shown in Figure 5, the printing and impression cylinders I, 2 are in the usual manner geared together by gear wheels 24, 25 and the printing cylinder is driven by a gear wheel 28 in mesh with a driving gear 21 which would be in drive connection with an associated printing coup le (not shown) so that the couple formed by the cylinders I, 2 would run in synchronism with the associated couple. Thus, in order to turn the cylinder 2 with respect to the cylinder I it is necessary to disconnect the cylinder 2 from the gear 25: This is effected by a clutch of the positive register type and having two positions spaced through an angle equal to the angle (120 as described) through which the cylinder 2 has to be turned with respect to the cylinder I. This clutch is diagrammatically indicated at 28 in Figure 5 and in detail in Figures 6 and '7: In these latter figures the impression cylinder shaft 29 is formed with a key 30 on which is slidably mounted one part 3I of the clutch: This part haslugs 32 to each of which is secured bushes 33 having apertures therein, the apertures being spaced, in diametrical pairs, at an angle 6 which is equal in the example given to 120. The other part of the clutch is formed by a part 34 which is freely mounted on the shaft 29 and forms part of the gear wheel 25, this part 34 having two diametrically opposite driving pins 35: The part 3| is provided with a circumferential groove 36 into which extends a roller 3! on an arm 38 secured to a spindle 39 having an operating handle 43. Thus by rocking the arm 38 the roller causes the part 3! to slide either to the left or right, movement to the right causing that pair of bushes 33 which engage the pins 35 to leave the pins and thereby effecting disconnection of the clutch: When the clutch is thus disconnected, the shaft 29 and the impression cylinder 2 can be turned with respect to the plate cylinder I so as tobring the other pair of bushes in line with the pins: By thus moving the part M to the left, this other pair of bushes can be caused to engage the pins thus positively clutching the impression and plate cylinders in the new position representing an adjustment of In order to lock the clutch in its clutching position, the spindle 39 is provided with an aperture to receive a removable locking pin 4!.

A second clutch d2 similar to that described is provided. for enabling the couple constituted by the two cylinders I, 2 to be adjusted together with respect to the associated couple so that compensation can be made for the length of the web run from one couple to the other as compared with the length of the run when the direction of lead of the web is reversed, this require ment being well known to those versed in the art and therefore requiring no further description.

The gear wheel 25 is formed in two parts one 43 having the gear wheel 25 and the other (previously referred to as 34) connected thereto by bolts M screwing into the part 43 and passing through arcuate slots 45 formed in the part 34. This arrangement enables a small adjustment of the cylinder 2 to be made with respect to the cylinder 3 by slackening the bolts 44, operating an adjusting bolt screwed into a lug ll on the part 43, and engaging surfaces 43 formed on the part 3% to turn the cylinder 2 through the desired angle and reclamping by means of the bolts 44,

While as has previously been stated it is preferred to provide for the adjustment of the margin bars in the usual manner, 1. e. by employing detachable bars as has been referred to, it would be possible toarrange for the positions of the bars to be interchanged in the manner described with reference to the filling pieces in the impression cylinder, 1. e. by providing the plate cylinder with guides in which the margin bars can slide so as to interchange position.

What I claim is:--

1. A reversible printing cylinder, a first set of margin bars, a second set of margin bars in staggered relation with the said first set, said cylinder having a plurality of seats for each bar of said second set, each bar of said second set having means for securing it selectively to any of the seats, whereby the second set of bars may be selectively positioned to reverse the angle of stagger to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and the ends of which are received within longitudinal recesses in the impression cylinder, the recesses being spaced circumferentially of the impression cylinder through an angle equal to the angle of stagger and being equal in number to the number of sets of margin bars, filling pieces in at least certain of the recesses and having such length relative to the length of the recesses in which they are mounted as to leave open a length of recess equal to the length of a margin bar, and means for securing the filling pieces to resist endwlse movement in the recesses.

2. A reversible printing cylinder, a first set of margin bars, a second set of margin bars in staggered relation with the said first set, said cylinder having a plurality of seats for each bar of said second set, each bar of said second set having means for securing it selectively to any of the seats, whereby the second set of bars may be selectively positioned to reverse the angle of stagger to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and having their ends received within two coextensive longitudinal recesses which are formed in the cylinder and are spaced apart through an angle equal to the angle of stagger of the margin bars, filling pieces in the recesses and having such length as to leave open at opposite ends of the recesses a length of recess equal to the length of a margin bar, and means for securing the filling pieces to resist movement in their recesses, whereby the open parts of the recesses can be reversed to correspond to reversal of the stagger of the margin bars.

A reversible printing cylinder, staggered sets of margin bars, means so mounting the margin bars on the cylinder that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and the ends of which are received Within longitudinal recesses in the impression cylinder, the recesses being spaced circumferentially of the impression cylinder through an angle equal to the angle of stagger and being equal in number to the number of sets of margin bars, filling pieces in at least certain of the recesses and having such length relative to the length of the recesses in which they are mounted as to leave open a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in the recesses, thus enabling the open parts of the recesses to be reversed to correspond to reversal of the margin bars, and a clutch device interconnecting the two cylinders and having two clutching positions one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses.

4. A reversible printing cylinder, two staggered sets of margin bars on the cylinder, means so mounting the bars that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and having their ends received Within two coextensive longitudinal recesses which are formed in the cylinder and are spaced apart through an angle equal to the angle of stagger of the margin bars, filling pieces in the recesses and having such length as to leave open at opposite ends or" the recesses a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in their recesses whereby the open parts of the recesses can be reversed to correspond to reversal of the stagger of the margin bars, and a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the re" versed bars and the reversed open parts of the recesses 5. A reversible printing cylinder, staggered sets of margin bars, means so mounting the margin bars on the cylinder that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and the ends of which are received within longitudinal recesses in the impression cylinder, the recesses being spaced circumferentially of the impression cylinder through an angle equal to the angle of stagger and being equal in number to the number of sets of margin bars, filling pieces in at least certain of the recesses and having such length relative to the length of the recesses in which they are mounted as to leave open a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in the recesses, thus enabling the open parts of the recesses to be reversed to correspond to reversal of the margin bars, two blanket straining devices associated with each recess and located on opposite sides thereof, and a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses.

6. A reversible printing cylinder, two staggered sets of margin bars on the cylinder, means so mounting the bars that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and having their ends received within two coextensive longitudinal recesses which are formed in the cylinder and are spaced apart through an angle equal to the angle of stagger of the margin bars, filling pieces in the recesses and having such length as to leave open at opposite ends of the recesses a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in their recesses whereby the open parts of the recesses can be reversed to correspond to reversal of the stagger of the margin bars, two blanket straining devices associated with each recess and located on opposite sides thereof, and a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses.

'7. A reversible printing cylinder, staggered sets of margin bars, means so mounting the margin bars on the cylinder that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and the ends of which are received within longitudinal recesses in the impression cylinder, the recesses being spaced circumferentially of the impression cylinder through an angle equal to the angle of stagger and being equal in number to the number of sets of margin bars, filling pieces in at least certain of the recesses and having such length relative to the length of the recesses in which they are mounted as to leave open a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in the recesses, thus enabling the open parts of the recesses to be reversed to correspond to reversal of the margin bars, a clutch device interconnecting the twocylinders and having two clutching positions, one providing register between the bars and the open parts of the recessesin one position thereof and the other position providing a register between the reversed bars and the reversed open parts of the recesses, a second printing cylinder and a second impression cylinder operating, on a web which is also operated on by the first printing cylinder and impression cylinder, and a second clutch device interconnecting the first andv second cylinders and having two clutching positions, one of which provides register between the first and second cylinders when the web is led in one direction and the other position providing registerwhen the web is led in the other direction.

8. A reversible printing cylinder, two staggered sets of margin bars on the cylinder, means so mounting the bars that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and having their ends received within two coextensive longitudinal recesses which are formed in the cylinder and are spaced apart through an angle equal to the angle of stagger of the margin bars, filling pieces in the recesses and having such length as to leave open at opposite ends of the recesses a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in their recesses whereby the open parts of the recesses can be reversed to correspond to reversal of the stagger of the margin bars, a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses, a second printing cylinder and a second impression cylinder operating on a web which is also operated on by the first printing cylinder and impression cylinder, and a second clutch device interconnecting the first and second cylinders and having two clutching positions, one of which provides register between the first and second cylinders when the web is led in one direction and the other position providing register when the web is led in the other direction.

9. A reversible printing cylinder, staggered sets of margin bars, means so mounting the margin bars on the cylinder that the angle of stagger is reversible to correspond to reverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and the ends of which are received within longitudinal recesses in the impression cylinder, the recesses being spaced circumferentially of the impression cylinder through an angle equal to the angle of stagger and being equal in number to the number of sets of margin bars, filling pieces in at least certain of the recesses and having such length relative to the length of the recesses in which they are mounted as to leave open a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in the recesses, thus enabling the open parts of the recesses to be reversed to correspond to reversal of the margin bars, two blanket straining devices associated with each recess and located on opposite sides thereof, a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses, a second printing cylinder and a second impression cylinder operating on a web which is also operated on by the first printing cylinder and impression cylinder, and a second clutch device interconnecting the first and second cylinders and having two clutching positions one of which provides register between the 10 first and second cylinders when the web is led in one direction and the other position providing register when the web is led in the other direction.

10. A reversible printing cylinder, two staggered sets of margin bars on the cylinder, means so mounting the bars that the angle of stagger is reversible to correspond toreverse rotation of the cylinder, a reversible impression cylinder, blankets around the impression cylinder and havgoing their ends received within two coextensive longitudinal recesses which are formed in the cylinder and are spaced apart through an angle equal to the angle of stagger of the margin bars, filling pieces in the recesses and having such :15 length as to leave open at opposite ends of the recesses a length of recess equal to the length of a margin bar, means mounting the filling pieces for movement in their recesses whereby the open parts of the recesses can be reversed to correspond to reversal of the stagger of the margin bars, two blanket straining devices associated with each recess and located on opposite sides thereof, a clutch device interconnecting the two cylinders and having two clutching positions, one providing register between the bars and the open parts of the recesses in one position thereof and the other position providing register between the reversed bars and the reversed open parts of the recesses, a second printing cylinder and a second impression cylinder operating on a web which is also operated on by the first printing cylinder and impression cylinder, and a second clutch device interconnecting the first and second cylinders and having two clutching positions one of which provides register between the first and second cylinders when the web is led in one direction and the other position providing register when the web is led in the other direction. 

